Given a connected and undirected graph, a spanning tree of that graph is a subgraph that is a tree and connects all the vertices together. A single graph can have many different spanning trees. A minimum product spanning tree for a weighted, connected and undirected graph is a spanning tree with weight product less than or equal to the weight product of every other spanning tree. The weight product of a spanning tree is the product of weights corresponding to each edge of the spanning tree. All weights of the given graph will be positive for simplicity.
This problem can be solved using standard minimum spanning tree algorithms like krushkal and prim’s algorithm, but we need to modify our graph to use these algorithms. Minimum spanning tree algorithms tries to minimize total sum of weights, here we need to minimize total product of weights. We can use property of logarithms to overcome this problem.
As we know,
log(w1* w2 * w3 * …. * wN) = log(w1) + log(w2) + log(w3) ….. + log(wN)
We can replace each weight of graph by its log value, then we apply any minimum spanning tree algorithm which will try to minimize sum of log(wi) which in-turn minimizes weight product.
For example graph, steps are shown in below diagram,
In below code first we have constructed the log graph from given input graph, then that graph is given as input to prim’s MST algorithm, which will minimize the total sum of weights of tree. Since weight of modified graph are logarithms of actual input graph, we actually minimize the product of weights of spanning tree.
Edge Weight 0 - 1 2 1 - 2 3 0 - 3 6 1 - 4 5 Minimum Obtainable product is 180
This article is contributed by Utkarsh Trivedi. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to email@example.com. See your article appearing on the GeeksforGeeks main page and help other Geeks.
Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.
- Kruskal's Minimum Spanning Tree using STL in C++
- Boruvka's algorithm for Minimum Spanning Tree
- Applications of Minimum Spanning Tree Problem
- Prim’s Minimum Spanning Tree (MST) | Greedy Algo-5
- Reverse Delete Algorithm for Minimum Spanning Tree
- Kruskal’s Minimum Spanning Tree Algorithm | Greedy Algo-2
- Computer Network | Types of Spanning Tree Protocol (STP)
- Maximum Possible Edge Disjoint Spanning Tree From a Complete Graph
- Problem Solving for Minimum Spanning Trees (Kruskal’s and Prim’s)
- Maximum product of two non-intersecting paths in a tree
- Minimum Operations to make value of all vertices of the tree Zero
- Roots of a tree which give minimum height
- Total number of Spanning Trees in a Graph
- Total number of Spanning trees in a Cycle Graph
- Product of lengths of all cycles in an undirected graph